Birth and marriage certificates were issued to individuals. Census returns were not issued to anyone.
A census was a snapshot of one night in ten years and proves very little. It’s not a legal document.
Anyone trying to prove entitlement to citizenship would be better off obtaining the appropriate birth, death and marriage certificate/s, accurate or not.
It is very doubtful that the original Scottish, English and Welsh censuses can be accessed by the public, however the OP might like to chase up whichever authority holds them and ask the question.
They may also like to explain the situation to whichever country they are applying for citizenship of, and ask if the online copy of the census is acceptable if access to originals is denied.